Integrated processes and systems for reforming and isomerizing hydrocarbons

ABSTRACT

Processes and systems are provided for reforming and isomerizing hydrocarbons to produce octane upgraded hydrocarbons. The process involves providing a reforming feedstream to a reforming zone containing a reforming catalyst and operating the reforming zone at reforming conditions including reforming pressure in a range of from about 1 to about 18 atmospheres to generate a reforming zone effluent. The reforming zone effluent is separated to form a net gas stream comprising primarily hydrogen and a liquid reforming product stream, and then providing the net gas stream and an isomerization feedstream to an isomerization zone containing an isomerization catalyst. The isomerization zone is operated at an isomerization pressure that is greater than the reforming pressure, to produce an isomerization zone effluent. The system for reforming and isomerizing hydrocarbons includes a reforming zone containing a reforming catalyst, a reforming separator, an isomerization zone containing an isomerization catalyst, and an isomerization separator.

TECHNICAL FIELD

The present disclosure generally relates to processes and systems forconversion of hydrocarbons and, more particularly, relates to integratedprocesses and systems for reforming and isomerizing hydrocarbons toproduce aromatic and branched hydrocarbons.

BACKGROUND

Catalytic reforming and catalytic isomerization are two widely usedprocesses for “upgrading” hydrocarbons, i.e., rearranging the structureof the hydrocarbons so they are useful for blending and formulation ofhigh octane gasoline products. The traditional gasoline blending poolnormally includes C₄ and heavier hydrocarbons having boiling points ofless than 205° C. (401° F.) at atmospheric pressure. Preferably, highoctane gasoline products have an octane rating, more specifically aResearch Octane Number (RON), of from about 90 to about 101.

Mixtures of hydrocarbons comprising primarily C₇ and heavierhydrocarbons may be octane upgraded by reforming, which means convertingparaffin and naphthene hydrocarbons to aromatic hydrocarbons. On theother hand, C₅ hydrocarbons (i.e., pentane) are not readily convertedinto aromatics and, therefore, normal C₅ hydrocarbons are typicallyoctane upgraded by converting them to branched-chain C₅ hydrocarbons.Furthermore, while normal C₆ hydrocarbons (i.e., hexane) may be reformedto C₆ aromatic hydrocarbons, i.e., benzene, the health concerns relatedto benzene make isomerization of C₆ hydrocarbons to branched-chain C₆hydrocarbons preferable to reforming. Accordingly, in industry practice,the octane number of C₅-C₆ hydrocarbons (i.e., C₅-C₆ paraffins) isgenerally upgraded by isomerizing the straight chain hydrocarbonsthereof to form branched-chain C₅-C₆ hydrocarbons (i.e., branched C₅-C₆paraffins) such as isopentane, dimethylbutane and methylpentane.

Combination processes involving reforming and isomerization of naphtharange feedstocks have been developed. In some such processes, suchfeedstocks are first subjected to reforming, followed by separation of aC₅-C₆ paraffin fraction from the reformate product, then isomerizing theC₅-C₆ paraffins fraction to upgrade the octane number of thesecomponents and recovering a C₅-C₆ isomerate liquid which may be blendedwith the reformate product. Other combination processes first subjectthe naphtha range feedstock to distillation to produce separatefractions, including a lighter fraction which is fed to theisomerization zone and a heavier fraction that is provided to thereforming zone. Sometimes the reformate product of such combinedprocesses is subjected to further separation and conversion, whichproduces additional C₅-C₆ paraffins for recycling to the isomerizationzone.

Various aspects inherent in each of the reforming and isomerizationreactions have been the basis of modifications to combined processesthat enhance their integration and reduce the amount and/or size ofrequired apparatus. For example, since the reforming reaction is ahydrogen-producing reaction, the effluent from a reforming zone containshydrogen, which, after separation, may be provided to the isomerizationzone thereby reducing the amount of fresh hydrogen feed required.Accordingly, in some modified combination processes the reforming andisomerization effluents are combined and then a hydrogen-containingstream is separated from the combined effluent stream and recycled tothe isomerization zone. Since existing combination processes stillrequire significant quantities of raw materials and energy, as well as amyriad of equipment and devices that, in turn, require substantiallysized areas for installation and operation, improvements that furtherincrease efficiency would be welcomed by industry. For example, furtherreduction of raw material and energy consumption through additionalreuse and recycle of material streams among process units in the system,or providing material streams and energy to other processes and systemsthat might otherwise be discarded as by-product or waste may furtherincrease efficiency. Also, by reducing the number and size of apparatusrequired to generate products of equivalent quality through eliminatingunnecessary separation, recycle or purification steps, capital costs aswell as the size of the required footprint of the overall system may bereduced.

Accordingly, it is desirable to provide integrated processes and systemsfor reforming and isomerizing hydrocarbons to more efficiently produceoctane upgraded aromatic and branched hydrocarbons. In addition, it isdesirable to provide integrated processes and systems that require fewerprocess steps and fewer system apparatus while still producinghydrocarbons having improved octane numbers. Furthermore, otherdesirable features and characteristics of the integrated processes andsystems contemplated herein will become apparent from the subsequentdetailed description of the invention and the appended claims, taken inconjunction with the accompanying drawings.

BRIEF SUMMARY

Processes and systems for reforming and isomerizing hydrocarbons areprovided. In an exemplary embodiment, a process includes the steps of:providing a reforming feedstream to a reforming zone containing areforming catalyst; operating the reforming zone at reforming conditionsthat comprise a reforming pressure in a range of from about 1 to about18 atmospheres to generate a reforming zone effluent; separating thereforming zone effluent to form a net gas stream comprising primarilyhydrogen and a liquid reforming product stream; providing the net gasstream and an isomerization feedstream to an isomerization zonecontaining an isomerization catalyst; and operating the isomerizationzone at isomerization conditions that comprise an isomerization pressurethat is greater than the reforming pressure, to produce an isomerizationzone effluent.

Another embodiment of the process provides a process for reforming andisomerizing hydrocarbons, comprising the steps of: providing a reformingfeedstream to a reforming zone containing a reforming catalyst;operating the reforming zone at reforming conditions that comprise areforming pressure in a range of from about 1 to about 18 atmospheres togenerate a reforming zone effluent; and separating the reforming zoneeffluent to form a net gas stream comprising primarily hydrogen and aliquid reforming product stream. In this embodiment, the process furtherincludes compressing the net gas stream; providing the net gas streamand an isomerization feedstream to an isomerization zone containing anisomerization catalyst; operating the isomerization zone with a singlepass through of the net gas stream and at isomerization conditions thatcomprise an isomerization pressure that is greater than the reformingpressure and is in a range of from greater than about 18 to about 70atm, to produce an isomerization zone effluent; and separating theisomerization zone effluent to form a total net gas stream and a liquidisomerization product stream. Additionally, at least a portion of thetotal net gas stream is compressed to form compressed total net gas, thesteps of compressing the net gas stream and compressing at least aportion of the total net gas stream are performed using a single powersource to operate independent compressors to compress each of the netgas and total net gas streams.

In still another embodiment, a system is provided for reforming andisomerizing hydrocarbons that includes: a reforming zone configured forcontaining a reforming catalyst and having a reforming feedstream inletand a reforming zone effluent outlet; a reforming separator having aninlet in fluid communication with the reforming zone effluent outlet ofthe reforming zone and having at least a net gas outlet and a liquidreforming product outlet; an isomerization zone configured forcontaining an isomerization catalyst and having an isomerizationfeedstream inlet, a net gas inlet in fluid communication with the netgas outlet of the reforming separator, and an isomerization zoneeffluent outlet; an isomerization separator having an inlet incommunication with the isomerization zone effluent outlet of theisomerization zone and having a total net gas outlet and a liquidisomerization product outlet.

BRIEF DESCRIPTION OF THE DRAWINGS

The processes and systems contemplated herein will hereinafter bedescribed in conjunction with the following FIGURE which is a schematicdiagram of an exemplary embodiment of the integrated processes andsystems described herein for reforming and isomerizing hydrocarbons.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and isnot intended to limit the processes and systems disclosed herein or theapplication and uses of the processes and systems. Furthermore, there isno intention to be bound by any theory presented in the precedingbackground or the following detailed description.

Generally, the processes and systems contemplated herein and describedin further detail below are integrated processes and systems forconcurrently reforming and isomerizing hydrocarbons to efficientlyproduce hydrocarbons having improved octane numbers. The presentlydescribed processes and systems for concurrently reforming andisomerizing hydrocarbons are integrated in various ways relating tostreamlining the process streams and reducing the amount of systemapparatus required to convert hydrocarbons to higher octanehydrocarbons.

Exemplary embodiments of the integrated processes and systems forreforming and isomerizing hydrocarbons will now be described withreference to the FIGURE. The FIGURE is a schematic diagram of anexemplary embodiment of a system 10 for reforming and isomerizinghydrocarbons. More particularly, in one exemplary embodiment, areforming feedstream 12 is provided to a reforming zone 14 containing areforming catalyst (not shown per se). The reforming and isomerizationzones 14, 18 are generally operated concurrently. Furthermore, as shownin the FIGURE, the reforming zone 14 typically includes a reformingreactor 20 configured for containing a reforming catalyst and having areforming feedstream inlet 22 and a reforming zone effluent outlet 24.

It should be understood that, although not shown in the FIGURE ordescribed in great detail herein, the reforming zone 14, as well asother process zones to be described hereinafter, are not limited to asingle reaction or other process vessel, but rather, each zone includesany and all typical apparatus required for, and ancillary to, performingthe desired process. Such apparatus includes for example, but withoutlimitation: reaction vessels, conduits, heat exchangers, mass exchangevessels, separation vessels, reboilers, recycle conduits, valves,temperature measurement and control apparatus, safety devices,condensers, compressors, etc. Furthermore, the process zones are notlimited to one of any type of apparatus. Although not shown per se inthe FIGURE, the reforming zone 14, for example, may comprise a pluralityof reforming vessels or reactors (see, e.g., reforming reactor 20), eachcontaining a reforming catalyst, as well as one or more heaters,conduits, valves, etc. Furthermore, although not shown, in someembodiments of the processes and apparatus described herein, thereforming zone 14 may also include a heat exchanger for heating thereforming feedstream 12 prior to entry into the reforming zone 14.

Furthermore, a wide variety of reforming zone feedstreams 12 may beused. In general, the reforming zone feedstream 12 contains primarilyfrom about C₇ to about C₁₂ hydrocarbons with a boiling point range fromabout 82 to about 240° C. As with most mixtures of hydrocarbons,refining and other processes tend to concentrate the desired species ofhydrocarbon in the mixture based on its intended use or anticipatedfurther processing, but these mixtures quite often contain some smallamount of hydrocarbon species in addition to those desired. This is onereason why hydrocarbon mixtures are often characterized by boilingranges instead of or in addition to a range of hydrocarbon speciescontained therein. Accordingly, it should be understood that, as usedherein, a mixture of hydrocarbons or a hydrocarbon stream described ascontaining or comprising “primarily” a specified hydrocarbon or range ofcarbon-numbered hydrocarbons means that the mixture or stream ofhydrocarbons being described may also contain very small amounts ofhydrocarbons besides the specified hydrocarbon or outside the statedcarbon number range, without altering the general characteristics (e.g.,boiling point) of the mixture or stream of hydrocarbons being described.

For example, the description that the reforming zone feedstream 12contains “primarily” from about C₇ to about C₁₂ hydrocarbons with aboiling point range from about 82 to about 240° C. means that thereforming zone feedstream 12 contains at least 70 weight percent ofhydrocarbon molecules each having from about 7 to about 12 carbon atomswith, possibly, very small amounts of hydrocarbon molecules each havingless than about 7 carbon atoms, as well as very small amounts ofhydrocarbon molecules each having more than 12 carbon atoms, such thatthe boiling point remains in the range of from about 82 to about 240° C.Similarly, the description that a net gas stream comprises primarilyhydrogen means that the net gas stream contains at least 70 weightpercent of hydrogen with, possibly, very small amounts of hydrocarbonmolecules each having one or two, or more, carbon atoms.

Generally, suitable reforming zone feedstreams may be generated fromvarious hydrocarbon sources using various separation techniques such asare known now, or in the future. As understood by persons of ordinaryskill in the relevant art, there are many possible hydrocarbon sourcesincluding, without limitation, crude oil from oil and gas extractionactivities, hydrocarbon fractions produced during crude oil refiningactivities, condensate streams generated by hydraulic fracturingactivities, recycled hydrocarbons derived from recovery and processingof used hydrocarbon products, as well as the many intermediatehydrocarbon products and streams that are produced during processing ofthe aforesaid hydrocarbon sources. Hydrocarbon mixtures containingprimarily C₇-C₁₂ hydrocarbons with a boiling point range from about 82to about 240° C. that are suitable for use as reforming zone feedstreams12 often result from processing the aforesaid hydrocarbon sources, aswell as those which may be discovered or developed in the future.

One example of a hydrocarbon stream suitable for use as a reforming zonefeedstream 12 may be derived from a full range naphtha feedstream thathas been produced by processing any of the hydrocarbon sources describedabove. Such a full range naphtha feedstream may contain primarily C₅-C₁₂hydrocarbons and have a boiling point from about 80 to about 240° C.,and is typically further separated into two or more refined fractionssuch as, without limitation: a light naphtha fraction, a heart-cutnaphtha fraction, and a heavy naphtha fraction. The light naphthafraction may contain primarily C₅ and C₆ hydrocarbons (i.e., pentane andhexane) and have a boiling point of from about 80 to about 140° C. Theheart-cut naphtha may contain primarily C₇-C₈ hydrocarbons and have aboiling point from about 130 to about 175° C., and preferably from about145 to 165° C. Finally, the higher-boiling heavy naphtha fraction maycontain primarily C₁₀ hydrocarbons, with significant quantities of C₉and C₁₁-C₁₂ hydrocarbons depending primarily on a petroleum refiner'soverall product balance. The boiling point of this heavy naphtha may befrom about 160 to about 240° C., and preferably from about 170 to about240° C.

With reference now back to the FIGURE, and as already stated, thereforming feedstream 12 suitable for use in connection with the system10 described herein comprise primarily C₇-C₁₂ hydrocarbons and have aboiling point range from about 82 to about 240° C. Such a reformingfeedstream 12 may, for example, comprise the heart-cut and heavy naphthafractions generated as described above.

The reforming zone 14 is operated at reforming conditions that typicallycomprise a reforming pressure in a range of from about 1 atmosphere toabout 18 atmospheres (absolute) (“atm”). For instance, withoutlimitation, the reforming pressure may be in a range of from about 1 toabout 15 atm, or from about 1 to about 10 atm, or from about 4 to about18 atm, or even from about 4 to about 12 atm, to generate a reformingzone effluent 26. Suitable operating temperatures for the reforming zone14 are generally in the range of from about 260 to about 560° C. Avariety of reactions occur in the reforming zone 14 including naphthenedehydrogenation and paraffin dehydrocyclization and isomerization,whereby the resulting reforming zone effluent 26 has an upgraded octanenumber. Hydrogen is generated within the reforming zone 14, butadditional hydrogen may be directed, if necessary, to the reforming zone14 in an amount sufficient to correspond to a ratio of from about 0.1 toabout 10 moles of hydrogen, total generated and added, per mole ofreforming feedstream 12.

The reforming feedstream 12 may be contacted with the reforming catalyst(not shown) in the reforming zone 14 in upflow, downflow, or radial-flowmode. The volume of the contained reforming catalyst corresponds to aliquid hourly space velocity of from about 1 to about 40 hr⁻¹. Thecatalyst is typically contained in a fixed-bed reactor or in amoving-bed reactor whereby catalyst may be continuously withdrawn andadded. Such configuration is associated with catalyst-regenerationoptions known to those of ordinary skill in the art, such as: (1) asemi-regenerative unit containing fixed-bed reactors that maintainoperating severity by increasing temperature, eventually shutting theunit down for catalyst regeneration and reactivation; (2) aswing-reactor unit, in which individual fixed-bed reactors are seriallyisolated by manifold arrangements as the catalyst become deactivated andthe catalyst in the isolated reactor is regenerated and reactivatedwhile the other reactors remain on-stream; (3) continuous regenerationof catalyst withdrawn from a moving-bed reactor, with reactivation andsubstitution of the reactivated catalyst, permitting higher operatingseverity by maintaining high catalyst activity through regenerationcycles of a few days; or: (4) a hybrid system with semi-regenerative andcontinuous-regeneration provisions in the same unit. A preferredembodiment includes a semi-regenerative fixed- bed reactor with catalystoperating at relatively low pressures to realize high yields of desiredC₅₊ hydrocarbon product associated with more moderate catalystdeactivation. As used herein, the term “C₅₊ hydrocarbon” includeslinear, branched and aromatic hydrocarbons having 5 or more carbon atomsin each molecule. In some embodiments, the total reforming effluent 26may be provided to a heat exchanger (not shown, but already mentionedabove) to exchange heat with the reforming feedstream 12.

The reforming catalyst (not shown per se in the FIGURE) is notparticularly limited and may be any catalyst capable of catalyzing theconversion of linear and branched C₇ and heavier hydrocarbons toaromatic C₇ and heavier hydrocarbons. As used herein, the term “C₇ andheavier hydrocarbons” includes linear, branched and aromatichydrocarbons having 7 or more carbon atoms in each molecule. Forexample, the reforming catalyst may comprise a supported platinum-groupmetal component. This component comprises one or more platinum-groupmetals, with a platinum component being preferred. The platinum mayexist within the catalyst as a compound such as an oxide, sulfide,halide, or oxyhalide, in chemical combination with one or more otheringredients of the catalytic composite, or as an elemental metal. Bestresults are obtained when substantially all of the platinum exists inthe catalytic composite in a reduced state. The preferred platinumcomponent generally comprises from about 0.01 to about 2 mass % of thecatalytic composite, preferably about 0.05 to about 1 mass %, calculatedon an elemental basis.

The catalyst may contain other metal components known to modify theeffect of the preferred platinum component. Such metal modifiers mayinclude Group IVA (14) metals, other Group VII (8-10) metals, rhenium,indium, gallium, zinc, uranium, dysprosium, thallium and mixturesthereof. In one embodiment, the metal modifier is a tin component.Catalytically effective amounts of such metal modifiers may beincorporated into the catalyst by any means known in the art.

In some embodiments, the reforming catalyst may be a dual-functioncomposite containing a metallic hydrogenation-dehydrogenation componenton a refractory support that provides acid sites for cracking andisomerization. The refractory support of such a reforming catalystshould be a porous, adsorptive, high-surface-area material which isuniform in composition without composition gradients of the speciesinherent to its composition. In an embodiment, refractory supportscontain one or more of: (1) refractory inorganic oxides such as alumina,silica, titania, magnesia, zirconia, chromia, thoria, boria or mixturesthereof; (2) synthetically prepared or naturally occurring clays andsilicates, which may be acid-treated; (3) crystalline zeoliticaluminosilicates, either naturally occurring or synthetically preparedsuch as FAU, MEL, MFI, MOR, MTW (IUPAC Commission on ZeoliteNomenclature), in hydrogen form or in a form which has been exchangedwith metal cations; (4) non-zeolitic molecular sieves,; (5) spinels suchas MgAl₂O₄, FeAl₂O₄, ZnAl₂O₄, CaAl₂O₄; and (6) combinations of materialsfrom one or more of these groups.

The reforming catalyst optimally contains a halogen component. Thehalogen component may be fluorine, chlorine, bromine, iodine or mixturesthereof. Chlorine is the preferred halogen component. The halogencomponent is generally present in a combined state with theinorganic-oxide support. The halogen component is preferably welldispersed throughout the catalyst and may comprise from more than about0.2 to about 15 mass %, calculated on an elemental basis, of the finalcatalyst.

In some alternative embodiments, the reforming catalyst may comprise alarge-pore molecular sieve, which is defined as a molecular sieve havingan effective pore diameter of about 7 angstroms or larger. Examples oflarge-pore molecular sieves which might be incorporated into the presentcatalyst include LTL, FAU, AFI and MAZ (IUPAC Commission on ZeoliteNomenclature) and zeolite-beta. In such embodiments, the reformingcatalyst contains a nonacidic L-zeolite (LTL) and an alkali-metalcomponent as well as a platinum-group metal component. In order to be“nonacidic,” the zeolite will have substantially all of its cationicexchange sites occupied by non-hydrogen species. Preferably the cationsoccupying the exchangeable cation sites will comprise one or more of thealkali metals including lithium, sodium, potassium, rubidium, cesium andmixtures thereof, with potassium being preferred, although othercationic species may be present. The L-zeolite should also be compositedwith a binder to provide a convenient form for use as a suitablereforming catalyst. Suitable binders include any refractory inorganicoxide binder such as one or more of silica, alumina or magnesia, forexample, without limitation.

Returning now to the FIGURE, the reforming zone 14 of the exemplaryembodiment of the system 10 now being described includes a separationzone 28. The reforming zone effluent 26 is separated in the separationzone 28 to form a net gas stream 30 comprising primarily hydrogen and aliquid reforming product stream 32. Upon leaving the separation zone 28,the liquid reforming product stream 32 comprises a gasoline fractionhaving an Research Octane Number (RON) in a range of from about 90 toabout 101 that can be separated out further downstream. As shown in theFIGURE, the separation zone 28 may comprise a reforming separator 28having an inlet 34 in fluid communication with the reforming zoneeffluent outlet 24 of the reforming reactor 20 and having at least a netgas outlet 36 and a liquid reforming product outlet 38.

As shown in the FIGURE, an isomerization feedstream 16 is provided to anisomerization zone 18 containing an isomerization catalyst (not shownper se). Furthermore, as shown in the FIGURE, the isomerization zone 18comprises an isomerization reactor 40 configured for containing anisomerization catalyst and having an isomerization feedstream inlet 42,a net gas inlet 44 in fluid communication with the net gas outlet 36 ofthe reforming separator 28, and an isomerization zone effluent outlet46.

The isomerization zone 18 also requires hydrogen. Since the net gasstream 30 derived from separation of the reforming effluent 26 compriseshydrogen, in accordance with the integrated processes and system 10described herein, the net gas stream 30 is provided to the isomerizationzone 18. The isomerization zone 18 is operated at isomerizationconditions to produce an isomerization zone effluent 48. Theisomerization zone effluent 48 typically comprises a mixture ofprimarily normal pentane, normal hexane, isopentane, dimethylbutane andmethylpentane and hydrogen, with smaller amounts of C₄ and lighterhydrocarbons, as well as small amounts of C₇ and heavier hydrocarbons.As used herein, the term “C₄ and lighter hydrocarbons” includes linearand branched hydrocarbons having 4 or fewer carbon atoms in eachmolecule.

The net gas stream 30 contains hydrogen derived at least in part fromreactions in the reforming zone 14, as well as smaller amounts of C₄ andlighter hydrocarbons and, therefore may advantageously be used tosupplement or replace an independent hydrogen source to theisomerization zone 18. Since the reforming zone 14 is operated at arelatively low pressure and the net gas stream 30 is not subjected torecontact with the liquid reforming product stream 32 as in someexisting processes, the net gas stream will also contain small amountsof C₅-C₇ and heavier hydrocarbons, The net gas stream 30 may be providedto the isomerization zone 18, either separately from the isomerizationfeedstream 16 (as shown), or by first mixing with the isomerizationfeedstream 16 and then providing the mixed stream to the isomerizationzone 18.

As explained previously, and while not shown specifically in the Figure,the isomerization zone 18 may include not only one or more isomerizationreactors 40, each containing isomerization catalyst, but also otherapparatus such as heaters, heat exchangers, conduits, valves,temperature measurement and control apparatus, safety devices, etc., asrequired for, and ancillary to, performing the desired isomerizationreaction. In the embodiment shown in the FIGURE, the isomerization zone18 also includes a separation zone 50 that receives the isomerizationzone effluent 48 and produces a total net gas stream 52 and a liquidisomerization product stream 54. More particularly, as shown in theFIGURE, the separation zone 50 may include an isomerization separator 50having an inlet 56 in communication with the isomerization zone effluentoutlet 46 of the isomerization reactor 40 and having a total net gasoutlet 58 and a liquid isomerization product outlet 60.

The total net gas stream 52 derived from the isomerization zone effluent48 comprises primarily hydrogen from the reforming zone effluent 26 andnot consumed in the isomerization zone 18. The liquid isomerizationproduct stream 54 also derived from the isomerization zone effluent 48typically comprises a mixture of primarily normal pentane, normalhexane, isopentane, dimethylbutane and methylpentane.

As another example of ancillary apparatus that is typically included inthe isomerization zone 18, while not shown in the FIGURE, a controlvalve may be included to meter the addition of hydrogen to theisomerization zone 18 directly, or to the isomerization feedstream 16prior to entry into the isomerization zone 18. The hydrogenconcentration in the isomerization zone effluent 48 or one of the outletstream fractions derived therefrom is monitored by a hydrogen monitor(also not shown) and the control valve setting position is adjusted tomaintain the desired hydrogen concentration. The hydrogen concentrationat the effluent is calculated on the basis of total effluent flow rates.The molar ratio of hydrogen to hydrocarbon in the isomerization zoneeffluent 48 should be from about 0.05 to about 5.0. Hydrogen will beconsumed in the isomerization zone 18, the net total of which is oftenreferred to as the stoichiometric hydrogen requirement associated with anumber of side reactions that occur. An amount of hydrogen in excess ofthe stoichiometric amounts for the side reactions may be maintained inthe isomerization zone 18 to provide good stability and conversion bycompensating for variations in feed stream compositions that alter thestoichiometric hydrogen requirements.

It is noted that other combined processes and systems for reforming andisomerizing hydrocarbons may generate a net gas stream for use as ahydrogen-containing feedstream by first combining a reforming zoneeffluent with an isomerization zone effluent and then separating thatcombined effluent stream to form a net gas stream comprising primarilyhydrogen and a combined liquid product stream. In such other combinedprocesses and systems, the resulting net gas stream may be provided tothe isomerization zone; however, the resulting net gas stream is oftenfirst purified to remove the non-hydrogen components therefrom andincrease the hydrogen concentration thereof. Such purification istypically accomplished by “recontacting” the combined effluent net gasstream with the combined liquid product stream one or more times priorto being provided to the isomerization zone. As is easily recognized,recontacting the net gas stream for purification requires additionalapparatus such as a cooler, a vessel and associated regenerationequipment for each stage of recontact. In contrast, the integratedprocesses and system 10 contemplated and described herein do not requirecombining the reforming and isomerization effluents 26, 48 prior toseparating and generating the net gas stream 30 comprising hydrogen and,furthermore, no recontacting of the net gas stream 30 is performed priorto providing the net gas stream to the isomerization zone 18. Withoutwishing to be bound in any way by theory, it is believed that somepurification of the net gas stream occurs in the present integratedprocesses and system 10 in the separation zone 50 that separates theliquid isomerization product stream 54 from the isomerization zoneeffluent 48. This means that some apparatus (cooler, vessel andassociated compression equipment) typically included in other combinedprocesses and systems are not necessary and do not need to be includedin the present integrated processes and systems.

Additionally, it is noted that the integrated processes and systemscontemplated and described herein operate the isomerization zone 18 witha single pass-through of the hydrogen/net gas stream 30. A singlepass-through of the hydrogen/net gas stream 30 means that there is noseparate recycle compressor required in the isomerization zone 18 torecycle hydrogen from the isomerization separator 50 to theisomerization reaction reactor 40. In other combined processes andsystems, the isomerization zone often includes separation of theisomerization zone effluent to form another net gas stream, at least aportion of which is recycled to the isomerization zone using additionalapparatus such as a recycle gas cooler, a recycle gas drier, conduitsand valves, none of which are necessary in the present integratedprocesses and systems.

Suitable isomerization feedstreams 16 comprise primarily C₅-C₆hydrocarbons, and more specifically, primarily C₅-C₆ normal paraffins.Some common hydrocarbon processing product streams useful as suchisomerization feedstreams 16 include, without limitation, light naturalgasoline, light straight run naphtha, gas oil condensate, lightraffinates, light reformate, light hydrocarbons, and straight rundistillates having a boiling point of less than about 100° C. andcontaining substantial quantities of C₄-C₆ paraffins. The light naphthafraction described earlier as derived from separation of a full rangenaphtha feedstream and containing primarily C₅-C₆ hydrocarbons (i.e.,pentane and hexane) and having a boiling point of from about 80 to about140° C. would, for example, serve advantageously as a suitableisomerization feedstream 16 for the integrated processes and systemsdescribed herein. These hydrocarbon processing product streams may bederived from any number of hydrocarbon sources, such as those describedearlier in connection with suitable reforming feedstreams 12.

The isomerization zone 18 is generally operated at isomerizationconditions that maximize the production of C₅-C₆ isoalkane products fromthe isomerization feedstream 16. In accordance with the integratedprocesses and systems contemplated and described herein, suchisomerization conditions comprise an isomerization pressure that isgreater than the reforming pressure in the reforming zone 14. Inaddition, suitable isomerization pressures are in a range of fromgreater than about 18 to about 70 atm (absolute). For instance, withoutlimitation, the isomerization pressure may be in a range of from greaterthan about 18 to about 50 atm, or from greater than about 18 to about 45atm, or from about 20 to about 50 atm, or even from about 20 to about 30atm, to generate the isomerization zone effluent 48.

Suitable operating temperatures for the isomerization zone 18 aregenerally in the range of from about 40 to about 235° C. Lower reactiontemperatures are generally preferred since they usually favorequilibrium mixtures of isoalkanes versus normal alkanes. Lowertemperatures are particularly useful in processing feeds composed of C₅and C₆ paraffin hydrocarbons where the lower temperatures favorequilibrium mixtures having the highest concentration of the mostbranched isoalkanes. When the isomerization feedstream 16 is primarilyC₅ and C₆ paraffin hydrocarbons, isomerization temperatures in the rangeof from about 60 to about 160° C. are preferred. The feed rate to theisomerization zone 18 may vary over a wide range. These conditionsinclude liquid hourly space velocities ranging from about 0.5 to about12 hr⁻¹, such as, for example, from about 1 and about 6 hr⁻¹.

The isomerization catalyst (not shown per se in the FIGURE) is notparticularly limited and may be any catalyst that is capable ofcatalyzing the conversion of linear C₅-C₆ hydrocarbons to branched C₅-C₆hydrocarbon isomers. For example, various catalysts comprising platinumand aluminum, with or without an additional halogen component, have beenknown to catalyze the isomerization of C₄-C₇ hydrocarbons. A highlyactive isomerization catalyst comprising alumina with from about 0.01 toabout 25 weight percent (wt %) platinum and from about 2 to about 10 wt% of a chloride component is capable of isomerizing C₄-C₇ hydrocarbonsin the presence of very little hydrogen. Another exemplary embodimentincludes a high chloride catalyst on an aluminum base containingplatinum. The aluminum is an anhydrous gamma-alumina with a high degreeof purity. The catalyst may also contain other platinum group metals,i.e., noble metals, excluding silver and gold, and selected from thegroup consisting of platinum, palladium, germanium, ruthenium, rhodium,osmium, and iridium. These metals demonstrate differences in activityand selectivity such that platinum has now been found to be the mostsuitable for this process. The platinum component may exist within thefinal catalytic composite as an oxide or halide or as an elementalmetal. The presence of the platinum component in its reduced state hasbeen found most advantageous.

Additionally, suitable isomerization catalysts include a type ofcatalyst that comprises a sulfated support of an oxide or hydroxide of aGroup IVB (IUPAC 4) metal, such as zirconium oxide, titanium oxide orhydroxide, at least a first component which is a lanthanide element oryttrium component, and at least a second component being aplatinum-group metal component. It is believed that these isomerizationcatalysts are more tolerant of the presence of sulfur and water in theisomerization zone 18. In particularly advantageous embodiments, thefirst component of such isomerization catalyst contains at leastytterbium and the second component is platinum. The lanthanide elementor yttrium component can be incorporated into the catalyst in any amountthat is catalytically effective, suitably from about 0.01 to about 10mass % lanthanide, or yttrium, or mixtures thereof, in the catalyst onan elemental basis. In one embodiment, about 0.5 to about 5 mass %lanthanide or yttrium is used, calculated on an elemental basis. Thesecond component, a platinum-group metal, may exist within the finalcatalytic composite as a compound such as an oxide, sulfide, halide,oxyhalide, etc., in chemical combination with one or more of the otheringredients of the composite or as the metal. Suitable amounts of theplatinum-group metal are in a range of from about 0.01 to about 2 wt %platinum-group metal component, on an elemental basis. It isparticularly advantageous when substantially all of the platinum- groupmetal is present in the elemental state. This isomerization catalystoptionally contains an inorganic-oxide binder, such as alumina. Thesupport, sulfate, metal components and optional binder may be compositedin any order effective to prepare a suitable isomerization catalyst.

Returning now to the FIGURE, in some embodiments of the system 10described herein, both the liquid reforming product stream 32 and theliquid isomerization product stream 54 are provided to a productseparation zone 62, such as a debutanizer. The liquid reforming productstream 32 and the liquid isomerization product stream 54 may be providedseparately to the product separation zone 62, or they may be firstcombined together and then provided to the product separation zone 62 asa single combined feedstream. The product separation zone 62 is operatedto generate a product stream 66 enriched in C₅ and heavier hydrocarbonsand an overhead stream 68 enriched in hydrogen, C₄ and lighterhydrocarbons. Conditions for the operation of the product separationzone 62 include pressures ranging from about 6 to about 40 atmospheres.Some embodiments utilize pressures from about 13 to about 34atmospheres. Suitable designs for rectification columns and separatorvessels suitable for the product separation zone 62 are well known tothose skilled in the art. As shown schematically in the Figure, theproduct separation zone 62 typically includes at least one combinedproduct separator 62 having an inlet 64 in fluid communication with boththe liquid reforming product outlet 38 of the reforming separator 28 andthe liquid isomerization product outlet 60 of the isomerizationseparator 50, and also having a product stream outlet 70 and an overheadstream outlet 100. As with other process zones, the product separationzone 62 may include one or more such separation columns or devices, aswell as a reboiler and various conduits, valves and control devices (notshown per se). The product stream 66 enriched in C₅ and heavierhydrocarbons may be subjected to further processing, such as separationsor gasoline blending.

In some exemplary embodiments, after the isomerization zone effluent 48has been separated to produce the total net gas stream 52 whichcomprises primarily hydrogen, at least a portion of the total net gasstream 52 is compressed to form compressed total net gas 72. As shown inthe FIGURE, the system 10 also includes a post-isomerization compressor74 for compressing the total net gas stream 52. The post-isomerizationcompressor 74 has a total net gas inlet 76 in fluid communication withthe total net gas outlet 58 of the isomerization separator 50 and acompressed total net gas outlet 78.

Prior to providing the total net gas stream 52 to the post-isomerizationcompressor 74, a portion 80 of total net gas stream 52 may be recycledby combining the portion 80 with the net gas stream 30 prior to thepost-reforming compressor 86. The compressed net gas (in stream 30)leaving the post-reforming compressor 86 is provided to theisomerization zone 18. It is noted that the recycled portion 80 of totalnet gas 52 is not purified by any separate process steps prior to beingrecycled to the isomerization zone 18. The remaining portion of thetotal net gas stream 52 (i.e., the portion not recycled) is provided tothe post-isomerization compressor 74 as already described. This partialtotal net gas recycle scheme may be useful, for example, when the netgas stream 30 derived from the reforming zone effluent 26 contains toolittle hydrogen to effectively operate the isomerization zone 18.

In another exemplary embodiment, at least another portion 102 of thecompressed total net gas 72 derived from the isomerization zone effluent48 is provided to a hydrogen-consuming process that is not already partof the integrated processes and systems contemplated and describedabove. While there are no particular limitations on the type ofhydrogen-consuming process that would benefit from receiving at least aportion 102 of the compressed total net gas stream, suchhydrogen-consuming processes may, for example, be a diesel hydrotreatingprocess 82, or a naphtha hydrotreating process 84, or both, as shown inphantom in the FIGURE.

In some embodiments, the net gas stream 30 derived from the reformingzone effluent 26 is compressed and then provided to the isomerizationzone 18. As shown in the FIGURE, the system 10 includes a post-reformingcompressor 86 having a net gas inlet 88 in fluid communication with thenet gas outlet 36 of the reforming separator 28 and a compressed net gasoutlet 90 in fluid communication with the net gas inlet 44 of theisomerization reactor 40. Furthermore, in some such embodiments, asshown in the FIGURE, the integrated system 10 has a single power source92 capable of operating the independent post-isomerization andpost-reforming compressors 74, 86, respectively, to separately compressthe total net gas stream 52 and the net gas stream 30 , respectively.The single power source 92, such as a single motor, and thepost-isomerization and post-reforming compressors 74, 86 may all bemounted on a multi-compressor apparatus, such as a frame or platform 94as shown schematically in the FIGURE. In this manner, a single powersource 92 is used to compress each of the net gas stream 30 and totalnet gas stream 52, thereby decreasing the amount of required apparatusfrom two power sources to one.

Additionally, in some embodiments, operating the diesel hydrotreatingprocess 82 generates a DHT recycle gas stream 96, which may becompressed and returned to the diesel hydrotreating process 82. In suchembodiments, a diesel recycle compressor 98 for compressing the DHTrecycle gas stream 96 may also be included on the multi-compressorapparatus 94, along with the other compressors 74, 86 and the singlepower source 92. In such an arrangement of apparatus, the single powersource 92 would be in communication with each of the compressors 74, 86,98 and capable of operating each separately and concurrently to compressthe respective streams 30, 52, 96, respectively. In this manner, asingle power source 92 would be used to compress each of the net gasstream 30, the total net gas stream 52, and the DHT recycle gas stream96, thereby decreasing the amount of required apparatus from three powersources to one. As will be easily recognized by persons of ordinaryskill, further embodiments of the integrated system contemplated anddescribed herein could include more than two or three independentcompressors mounted on the frame or platform 94 and operated by thesingle power source 92, thereby providing further capital cost andoperational savings.

While at least one exemplary embodiment has been presented in theforegoing detailed description of the invention, it should beappreciated that a vast number of variations exist. It should also beappreciated that the exemplary embodiment or exemplary embodiments areonly examples, and are not intended to limit the scope, applicability,or configuration of the methods and apparatus described herein in anyway. Rather, the foregoing detailed description will provide thoseskilled in the art with a convenient road map for implementing anexemplary embodiment of the methods and apparatus. It being understoodthat various changes may be made in the function and arrangement ofelements described in an exemplary embodiment without departing from thescope of the methods and apparatus as set forth in the appended claims.

What is claimed is:
 1. A process comprising the steps of: providing areforming feedstream to a reforming zone containing a reformingcatalyst; operating the reforming zone at reforming conditions thatcomprise a reforming pressure in a range of from about 1 to about 18atmospheres to generate a reforming zone effluent; separating thereforming zone effluent to form a net gas stream comprising primarilyhydrogen and a liquid reforming product stream; providing the net gasstream and an isomerization feedstream to an isomerization zonecontaining an isomerization catalyst; and operating the isomerizationzone at isomerization conditions that comprise an isomerization pressurethat is greater than the reforming pressure, to produce an isomerizationzone effluent.
 2. The process according to claim 1, wherein the step ofseparating the reforming zone effluent to form a liquid reformingproduct stream comprises forming a liquid reforming product stream witha Research Octane Number (RON) in a range of from about 90 to about 101.3. The process according claim 1, wherein the isomerization pressure isin a range of from greater than about 18 to about 70 atm.
 4. The processaccording to claim 1, wherein the step of operating the isomerizationzone is performed with a single pass-through of the net gas stream. 5.The process of claim 1, further comprising the step of separating theisomerization zone effluent to form a total net gas stream and a liquidisomerization product stream.
 6. The process according to claim 5,further comprising the steps of: providing both the liquid reformingproduct stream and the liquid isomerization product stream to aseparation zone; and operating the separation zone to generate a productstream enriched in C₅ and heavier hydrocarbons and an overhead streamenriched in C₄ and lighter hydrocarbons.
 7. The process according toclaim 5, further comprising the step of recycling at least a portion ofthe total net gas to the net gas stream prior to the step of providingthe net gas stream to the isomerization zone.
 8. The process accordingto claim 5, further comprising: compressing the net gas stream prior tothe step of providing the net gas stream to the isomerization zone; andcompressing at least a portion of the total net gas stream to formcompressed total net gas; wherein the steps of compressing the net gasstream and compressing at least a portion of the total net gas streamare performed using a single power source to operate independentcompressors to compress each of said streams.
 9. The process accordingto claim 8, further comprising the step of providing at least a portionof the compressed total net gas to a hydrogen-consuming process.
 10. Theprocess according to claim 9, wherein the hydrogen-consuming processcomprises a naphtha hydrotreating process, a diesel hydrotreatingprocess, or both.
 11. The process according to claim 9, wherein thehydrogen-consuming process comprises a diesel hydrotreating process, andthe process further comprises the steps of: operating the dieselhydrotreating process to generate a recycle gas stream; compressing therecycle gas stream; and recycling the recycle gas stream back to thediesel hydrotreating process; wherein the steps of compressing the netgas stream, compressing at least a portion of the total net gas stream,and compressing the recycle gas stream from the diesel hydrotreatingprocess are all performed using a single power source to operateindependent compressors to compress each of said streams.
 12. Anintegrated process for reforming and isomerizing hydrocarbons comprisingthe steps of: providing a reforming feedstream to a reforming zonecontaining a reforming catalyst; operating the reforming zone atreforming conditions that comprise a reforming pressure in a range offrom about 1 to about 18 atmospheres to generate a reforming zoneeffluent; separating the reforming zone effluent to form a net gasstream, comprising primarily hydrogen, and a liquid reforming productstream; compressing the net gas stream; providing the net gas stream andan isomerization feedstream to an isomerization zone containing anisomerization catalyst; operating the isomerization zone with a singlepass-through of the net gas stream and at isomerization conditions thatcomprise an isomerization pressure that is greater than the reformingpressure and is in a range of from greater than about 18 to about 70 atmto produce an isomerization zone effluent; separating the isomerizationzone effluent to form a total net gas stream and a liquid isomerizationproduct stream; and compressing at least a portion of the total net gasstream to form compressed total net gas, wherein the steps ofcompressing the net gas stream and compressing at least a portion of thetotal net gas stream are performed using a single power source tooperate independent compressors to compress each of the net gas andtotal net gas streams.
 13. A system for reforming and isomerizinghydrocarbons, the system comprising: a reforming reactor configured forcontaining a reforming catalyst and having a reforming feedstream inletand a reforming zone effluent outlet; a reforming separator having aninlet in fluid communication with the reforming zone effluent outlet ofthe reforming zone and having at least a net gas outlet and a liquidreforming product outlet; an isomerization reactor configured forcontaining an isomerization catalyst and having an isomerizationfeedstream inlet, a net gas inlet in fluid communication with the netgas outlet of the reforming separator, and an isomerization zoneeffluent outlet; an isomerization separator having an inlet incommunication with the isomerization zone effluent outlet of theisomerization zone and having a total net gas outlet and a liquidisomerization product outlet.
 14. The system according to claim 13,wherein the isomerization reactor comprises two or more isomerizationreactors, each capable of withstanding isomerization pressures of fromgreater than about 18 to about 70 atmospheres.
 15. The system accordingto claim 13, further comprising a post-reforming compressor having a netgas inlet in fluid communication with the net gas outlet of thereforming separator and a compressed net gas outlet in fluidcommunication with the net gas inlet of the isomerization reactor. 16.The system according to claim 15, further comprising apost-isomerization compressor having a total net gas inlet in fluidcommunication with the total net gas outlet of the isomerizationseparator, and a compressed total net gas outlet.
 17. The systemaccording to claim 16, further comprising a single power source whichprovides power for operating each of the post-reforming andpost-isomerization compressors.
 18. The system according to claim 17,further comprising a multi-compressor apparatus on which the singlepower source and each of the post-reforming and post-isomerizationcompressors are mounted and wherein each of the post-reforming andpost-isomerization compressors is in communication with the powersource.
 19. The system according to claim 18, wherein themulti-compressor apparatus further comprises a diesel recycle compressormounted thereon and also in communication with the power source, forcompressing a gaseous stream derived either from operation of the systemor operation of a another separate system.
 20. The system according toclaim 13, further comprising a combined product separator having aninlet in fluid communication with both the liquid reforming productoutlet of the reforming separator and the liquid isomerization productoutlet of the isomerization separator, and having a product streamoutlet and an overhead stream outlet.